Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1999-07-13
2001-06-26
Letscher, George J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06252745
ABSTRACT:
FIELD OF THE INVENTION
This application relates to magnetic disc drive assemblies and more particularly to an actuator arm crash stop/latch device.
BACKGROUND OF THE INVENTION
Various approaches have been developed to securely position an actuator arm assembly in a hard disc drive during a loss of power event or shutdown of the drive such that the heads land on and are retained on a portion of the disc real estate that does not contain data. Typically, these approaches involve either positioning the actuator arm onto a shelf to hold the heads away from the discs or positioning the heads over a portion of the disc surface that contains no data, such as the landing zones of the discs. The landing zone typically contains no magnetic recorded information or alternatively contains only historical servo information that is not pertinent to drive operation if damaged by the heads actually contacting the surface of the discs in this location. Approaches of holding the arm assembly in position include mechanical latches, electromechanical latches and magnetic latches. U.S. Pat. Nos. 5,568,333; 5,023,736; 5,483,399; 5,025,335 and 5,187,627 are representative of such latch devices.
To limit the range of motion of the actuator and heads under loss of power conditions and keep the heads in the landing zone, designers usually incorporate a crash stop with a latch mechanism to position and hold the arm in the park position while the drive is without power or actually turned off. One of the concerns in providing a resilient latch and crash stop device is the level of energy absorption by the latch device. It is desirable that the latch device absorb the impact of the actuator stopping without detrimentally affecting the head disc interface, even though the actuator arm is designed to stop in a position away from the data region of the discs where the heads are in a “park” position. If excessive impact were to occur, the heads or the disc surface itself could be damaged by head slap. Consequently crash stops may incorporate some type of rubber or elastomeric cushion and limit impact deflection so as to keep the heads from moving out of the landing zone onto the data region of the disc. Prior art stop designs incorporated little linear damping however, and sometimes the stop may deflect upward or downward from a direct impact line with the actuator tab (latching feature) because of its structural design and therefore may generate wear particles and/or generate undesirable resonances in the drive which can have undesirable effects on the head/disc interface in addition to resulting in excessive head movement.
SUMMARY OF THE INVENTION
Against this backdrop the present invention has been developed. The resilient linear latch and crash stop device in accordance with the present invention incorporates a magnetic latch and a linear impact absorbing crash stop into a single composite body made up of a magnet member for contacting a strike plate on the actuator arm, an energy absorbing member, and a latch base body assembled together wherein the energy absorbing member fastens the magnet member to the base body and absorbs impact energy in a generally linear fashion throughout the range of anticipated impact magnitudes. More particularly, the magnet member is fastened to a magnet support plate which is in turn fastened to the energy absorbing member. The energy absorbing member is an elastomeric body preferably formed in place and sandwiched between the magnetic mounting plate and the base body. The elastomeric body preferably has a vertically open, vertically symmetrical, tubular passage therethrough that preferably has a bell shaped horizontal cross sectional shape. The elastomeric body has a front end wall fastened to the magnet mounting plate, a rear end wall fastened to the base body, and a pair of spaced solid vertical side wall portions forming the vertical bell shaped tubular passage.
Each side wall portion has a thick side wall portion which provides directional stability to deflection of the magnet mounting plate during impact and a thin side wall portion preferably adjacent the front end wall which flexes to absorb the majority of impact forces of the actuator arm hitting the latch mechanism. After impact, the actuator arm is held fast with the strike plate against the domed head end of the latch magnet, until such time as the drive is again energized, and sufficient actuator arm motor force developed. The arm motor force must overcome the magnetic latching force and release the actuator for movement of the actuator arm and the read/write heads from the park position to the data portion of the rotating disc media.
The configuration of the elastomeric body having a vertical passage therethrough centered between the latch base body and the magnet mounting plate ensures that the impact forces received are linearly transmitted and absorbed. Consequently, there is minimal torsional distortion transmitted back into the actuator arm during deceleration and the result is a very cushioned and linear stopping of the actuator arm with the heads evenly decelerated to the park position. This results in minimal wear on the heads and disc surface at the park location and thus an increased longevity to the drive mechanism as a whole. These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.
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patent: 5483399 (1996-01-01), Jeong et al.
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patent: 0 383 551 (1990-08-01), None
Brent George Inslee
Deichert Richard Wayne
Kelsic Gary F.
Macpherson Aaron Steve
McReynolds Dave Paul
Letscher George J.
Merchant & Gould P.C.
Seagate Technology LLC
Wahl John R.
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